IN THE EAST CHINA SEA (AP) — Nearly two dozen Japanese nationalist activists and fishermen sailed on Sunday to a small group of islands at the center of a territorial dispute with China. They were closely monitored by Japan’s Coast Guard, but there were no Chinese patrols in the area and no incidents were reported.

After arriving in waters near the islands, those aboard the five fishing vessels carrying about 20 activists and fishermen began fishing but did not appear to have any plans to try to swim ashore, which is forbidden by the Japanese government and would be seen as a border violation by Beijing.

Both countries claim the uninhabited islands, known as the Senkaku in Japan and the Diaoyu in China, and have stepped up patrols to bolster their territorial claims. The dispute, which escalated rapidly after Japan moved last year to purchase them from a family who claimed to be their owner, has soured relations between the countries.

Japanese Coast Guard vessels monitored the ships closely, but an AP video journalist aboard one of them could not see any Chinese vessels. The trip was backed by Ganbare Nippon, a conservative and nationalist group, ostensibly to carry out a memorial ceremony at sea for about 80 civilians who died near the islets toward the end of World War II.

The outcroppings in the East China Sea are controlled by Japan but also claimed by China and Taiwan.

It is Ganbare Nippon’s fifth visit to the disputed areas this year, and the 15th time in the last three years. The organization says these trips are necessary to assert Japan’s claims to the islands.

China says the private owners had no legal claim to the islands, and strongly protested Tokyo’s purchase from them last September. Chinese marine surveillance ships have routinely been patrolling the waters around the islands since then. More recently, Beijing has been sending ships from the Chinese Coast Guard, which was formally inaugurated in July and gives Beijing greater latitude to patrol its claims by centralizing operations in a single body.

Japan has expressed unease about China’s activities near the islands and is bolstering its own surveillance capability — including plans to use drones capable of wide-range, high-altitude monitoring around the clock.

Activists from Hong Kong called off plans to sail for the disputed islands this week, according to Japan’s Kyodo news agency. Members of that group landed on one of the islets last year and raised Chinese and Taiwanese flags before being arrested by Japanese authorities.

No criminal charges were filed. But the landing of Chinese activists prompted Japanese activists to make similar efforts to assert Japan’s sovereignty.